A vibration correction device attempts to correct for vibrations in cameras caused by things such as handshaking by adjusting the tilt of the optical axis. The camera may then obtain clear images without blurring. In order to correct the vibration, the undesired angular velocity must be measured and a vibration correcting device must be employed to correct the vibration due to the undesired motions. Typically, an angular velocity detection sensor such as vibration gyro is adapted to detect the vibration, and the vibration correcting device uses a variable angle prism or movable lens system to correct the tilt of the optical axis caused by the vibration. However, imaging devices with conventional vibration correcting devices have several problems as described below.
For imaging devices or image pickup apparatuses, such as cameras, automation and multiplication are made in many functions such as auto exposure (AE) or auto focusing (AF). With increased complication and magnification, the vibration of the apparatus is a major factor in causing deterioration of the image quality. Even a small vibration may results in large vibrations in the image due to the long focal length and the narrow view angle for high magnification. Thus, several conventional vibration correcting devices have been designed.
There are mainly two methods to correct the vibration. One is electrical vibration correction, in which a vibration correcting program electrically corrects the amount of vibration from picked-up images obtained by an image sensor. The other method is optical vibration correction that corrects for vibration by correcting the tilt of optical axis due to the vibration. An angular velocity detection sensor such as vibration gyro is adapted to detect the vibration, and the optical vibration correcting device is employed to correct the vibration, as described in U.S. Pat. No. 6,734,902 B1. The optical vibration correction can be achieved by a variable angle prism or movable lens system.
Generally, optical vibration correction has advantages over electrical vibration correction. Since optical vibration correction removes the blurred image optically before the image sensor, it gives the clear images without blur. Also, because the optical vibration correction uses the pixels of the imaging sensor more effectively, it can provide better image quality. However, the conventional optical vibration correcting devices still have several problems. First, error in the correction of the picked-up image increases with an increase in the magnification of the image pickup lens. Second, macro mechanical motions are required. Third, they require complicated structures. Fourth, they have very low sampling frequencies. Fifth, they require a velocity detection sensor such as a vibration gyro.
FIGS. 1A–1C depict one embodiment of a prior art vibration correction device. FIG. 1A depicts the vibration correction device in operation when there is no vibration. FIG. 1B depicts the vibration correction device in operation with vibration but no correction. FIG. 1C depicts the vibration correction device in operation with vibration and correction. As depicted in FIGS. 1A–1C, the vibration correction device is located in an imaging device 11, such as a camera, video camera, or other type of imaging device. In the embodiment, the vibration correction device includes a lens 13, configured to focus an object image onto an image sensor 12. As shown in FIG. 1C, after the vibration amount is determined, the lens 13 is moved by macromovement to adjust the optical axis 14 of the lens 13. In other words, the system takes clear images when there is no vibration as shown in FIG. 1A. If there is vibration, the optical axis of the system is tilted by the vibration and the image sensor has the blurred image in FIG. 1B. From the obtained the angular velocity by the detecting sensor utilizing the vibration gyro, the vibration of imaging device is obtained and the lens system moves up, down, left, or right to correct the tilt of optical axis and the imaging device obtains the clear images without blur, as shown in FIG. 1C.
FIGS. 2A–2C depict one embodiment of a prior art vibration correction device using a variable angle prism. FIG. 2A depicts the vibration correction device in operation when there is no vibration. FIG. 2B depicts the vibration correction device in operation with vibration but no correction. FIG. 2C depicts the vibration correction device in operation with vibration and correction. In the embodiment depicted in FIGS. 2A–2C, a variable angle prism 23 is adjusted to change the optical axis 24 of the system, so that the image is focused onto the image sensor 22. The system also includes an auxiliary glass 21. In other words, in FIG. 2A, the optical axis is not tilted when there is no vibration. If there is vibration but it is not corrected, the tilt of optical axis results in the blurred image on the image sensor. By changing the refraction angle of prism with the vibration correction amount, the tilt of optical axis is corrected and the imaging device obtains the clear images, as shown in FIG. 2C.
Therefore, what is needed is an imaging stabilizer that does not require macromotions.